Esophageal stethoscopes were first described nearly three decades ago and have been in clinical use during anesthesia since then to enable the anesthesiologist to obtain a rather direct acoustic measure of the heart's performance. Such acoustic esophageal stethoscopes typically have comprised a tube or lumen which is inserted into the patient's esophagus to a location at which pressure variations due to heart and respiratory sounds are best transmitted to the interior of the lumen, by means such as a flexible diaphragm. The anesthesiologist is provided with an earpiece connected to the lumen by a suitable conduit, so that an acoustic indication of heart activity is provided. In some instances rather than an acoustic earpiece, the stethoscope has been provided with an electro-mechanical transducer, such as a piezo-electrical device, which produces a signal proportional to pressure variations in the lumen, the signal then being provided directly to a speaker or headset following amplification. In either case, determination of the actual cardiac pulse waveform, which is monitored for various reasons during surgery, has not been attempted via the esophageal stethoscope. Rather, external pressure transducers applied to the carotid artery or electro-optical transducers applied to the fingers have been relied on to determine cardiac pulse waveform. For many reasons, these external devices are either not useful on certain patients or are somewhat unreliable. Thus, a need has continued to exist for a simple, reliable cardiac pulse monitor which can be used on most patients while they are under anesthesia.